Structural Proteins

Presented by: Andrew and Briana

Structural Protein Overview

• Largest class of proteins (75% of the dry weight in humans)

• Generally add stiffness and rigidity to fluid biological components

• Commonly very fibrous• Provide support for both

large structures and microscopic structures

Microfilaments

Role in Living Things

• Keratin– Form strong supercoils– Protective function such as hair, nails, scales, feathers,

and beaks• Elastin

– Forms connective tissue (allows for stretching)– Tendons, ligaments, skin flexibility, lungs, arteries

• Myosin– Role in muscle movement such as hydrolysis of ATP

• Fibroin– Insoluble – Parallel sheets form silk used by insects and spiders

More Roles in Organisms

• Microtubules– Protein = Tubulin– Cytoskeleton, cellular movement, mitotic spindle

• Microfilaments– Protein = Actin– Cytoskeleton, muscle contraction, organelle movement

• Intermediate Filaments– Protein = Keratin– Cytoskeleton– Not involved directly

in movement

How do they function?

• Formation of fibers and filaments contribute to structural strength of proteins

• Movement and re-adjustment such as actin or elastin require ATP

• Other vitamins such as vitamin C are required for synthesis

Polymerization ATP Dependent

Shape and Function• Rigidity of Proteins

– Antiparallel chains form super coils– Hardened by hydrogen bonding and disulfide bridges

• Flexibility of Proteins– Solubility allows for globular proteins such as tubulin and actin to

form into strands– Lateral imperfect helix allows for elongation

• Transportation Ability– Polarization allows for transportation of molecules

• One negative and one positive end in the structure

Actin

F-Actin

Dissolve/Polymerize

Synthesis of Proteins

• Message sent to cell and genetic process begins

• Formation of mRNA (Units of 3)

Synthesis of Proteins Cont.

• Enters the cytoplasm

• Binds to a ribosome

Synthesis of Proteins Cont.

• tRNA brings the amino acid to the corresponding code on mRNA

• tRNA continues coming until chain is complete (peptide bonds)

Synthesis Miscellaneous

• Protein synthesis inhibitors such as the toxin ricin stops the production of protein

• Disruptions in translation can lead to mutations and a change in function (1 in 10,000)

• Example of such mutation is sickle cell (hemoglobin)

• Disruption of protein manufacture can be disastrous

Specific Example: Collagen

• The most abundant protein in mammals (25-35%)

• Plays a large role in body structure through ligaments and tendons (holds bones and muscles together)

• Vital for skin flexibility• Found in stiffer forms

such as bone

or cartilage

Collagen Structure

• 3 alpha peptide strands bonded together

• Forms a super helix or 3 part coil

• Glycine accounts for 1/3 of the structure to repeated pattern– No R-Group allows for

closer connection among helixes, so hydrogen bonding and linking is facilitated

• Formation of bundles impact function such as bone vs. ligaments (parallel or unparalleled)

Collagen Type 1 Helix

Collagen Genetics• Partial amino sequence: mhpglwlllv tlclteelaa ageksygkpc ggqdcsgscq

cfpekgargr pgpigiqgpt (repeat of g)• Similar to:

– Collagen alpha-6(IV) chain, partial [Macaca mulatta] 96%– Collagen alpha-6(IV) chain, partial [Macaca fascicularis] 96%

• Many others predicted relatedness to primates• Indicated a possible conserved gene which shows that many animals

may have had similar functional needs and the protein provided similar adaptive advantages

Collagen Disorders

• Non-Genetically Related– Osteoporosis, from old age, leads to inflexibility in

joints, thinner skin, and weaker bones• Genetically Related

– Osteogenesis imperfecta – Mutation leads to weak bones and irregular connective tissue

– Ehler-Danlos Syndrome – Varying mutations and effects such as rupture of arteries or deformed connective tissue

Impact of Osteogenesis imperfecta EDS Symptoms

In-Depth Disorder: Scurvy• Cause:

– Hydroxylation of lysines and prolines is a step that requires vitamin C as a cofactor. In scurvy, the lack of hydroxylation of prolines and lysines causes a looser triple helix (which is formed by 3 alpha peptides)

• Symptoms:– Spots on skin– Spongy gums– Loss of teeth– Pain in joints/Overall weakness

• Proposed Drug:– Target protein synthesis– A Vitamin C tablet that will provide necessary amounts of vitamins so

that collagen can form• Treatment applies to animals such as primates that cannot form their own

vitamin C. Other animals produce their own Vitamin C.

THANKS FOR LISTENINGFrom Andrew and Briana